Context:
In humans and many other animals, acid–base homeostasis is maintained by multiple mechanisms involved in three lines of defense:

1. Chemical:
   The first lines of defense are immediate, consisting of the various chemical bufferswhich minimize pH changes that would otherwise occur in their absence. These buffers include the bicarbonate buffer system, the phosphate buffer system, and the protein buffer system.[7]

2. Respiratory component:
   The second line of defense is rapid consisting of the control the carbonic acid concentration in the ECF by changing the rate and depth of breathing by hyperventilation or hypoventilation. This blows off or retains carbon dioxide (and thus carbonic acid) in the blood plasma as required.[5][8]

3. Metabolic component:
   The third line of defense is slow, best measured by the base excess,[9] and mostly depends on the renal system which can add or remove bicarbonate ions to or from the ECF.[5] Bicarbonate ions are derived from metabolic carbon dioxide which is enzymatically converted to carbonic acid in the renal tubular cells.[5][10][11] There, carbonic acid spontaneously dissociates into hydrogen ions and bicarbonate ions.[5] When the pH in the ECF falls, hydrogen ions are excreted into urine, while bicarbonate ions are secreted into blood plasma, causing the plasma pH to rise.[12] The converse happens if the pH in the ECF tends to rise: bicarbonate ions are then excreted into the urine and hydrogen ions into the blood plasma.
    

Please, read the document in entirety as to inform yourself in FULL CONTEXT. 

​

Elementally Energy personally noteworthy reiteration from 

​

Citation(s):

[1] https://en.wikipedia.org/wiki/Acid–base_homeostasis